Light Novels and Canon Representation
As Terry said, Light Novels are canon (only to those few delusional fans), who find that their characters portrayed in them have better feats than what they actually canonically have.
Relationship Updates
In Volume 23, Issei proposes to Asia, promising to make her happy and be by her side for eternity. Asia, filled with tears of joy, accepts Issei’s proposal, making her his fifth bride.
In a different world filled with peace and prosperity, Akeno Himejima and Issei Hyoudou never became servants of Rias Gremory; instead, the two of them became high school lovers and eventually ended up getting married and having kids.
Offspring Details
Kurobara ( 黒茨 くろばら ): Daughter of Issei and Kuroka.
Airi Hyoudou ( 兵藤 愛理 ひょうどう アイリ Hyōdō Airi): The second eldest of the siblings and the daughter of Issei and Asia Argento, she was born around the same year as Kurenai.
Miscellaneous
Watch High School DxD | Netflix.
Maybe you’ve been wondering about a new season. Fear not, High School DxD Season 5 is on its way! High School DxD is expected to be released in December 2021.
Kurenai Himejima is the first-born child of Issei Hyoudou, making him the oldest sibling, if Ophis is discounted. His mother is Akeno Himejima, from whom he inherits a lot of his powers.